This patent is directed to a burner assembly and a system for heating drying air, and, in particular, to a burner assembly and a system for heating drying air that produces low nitrogen oxide (NOx) emissions.
When fuel, such as natural gas, is burned or combusted, emissions are produced. Emissions from the combustion of natural gas, for example, may include carbon monoxide, carbon dioxide, nitrogen oxides (NOx), volatile organic compounds (VOCs), sulfur dioxide and particulate matter.
As to NOx emissions, it is believed that the principal mechanism of formation in natural gas combustion is thermal. The thermal NOx mechanism occurs through the thermal dissociation and subsequent reaction of nitrogen and oxygen molecules in the combustion air. The thermal NOx mechanism is influenced by the peak temperature of combustion, and the time of exposure of the combustion air to the peak combustion temperature.
NOx emissions can have undesirable effects on humans and the environment. In humans, low levels of NOx emissions can cause nausea, irritated eyes and/or nose, fluid forming in lungs and shortness of breath. Higher levels can lead to rapid, burning spasms, swelling of the throat, reduced oxygen intake, and increased fluid formation. As to the environment, NOx pollution may help form acid rain, and may combine with other pollutants to form toxic chemicals.
Steps have been taken to reduce NOx emissions through governmental regulation. For example, there are standards on NOx emissions produced by motor vehicles. In addition, there are standards for NOx emissions produced by commercial activities that require the combustion of natural gas.
For example, natural gas is typically used to heat the air used in painting booths. This air typically is introduced into the painting booths in large volumes, at high flow rates and at high temperatures. Consequently, the burners used to heat the air must operate at high peak combustion temperatures so as to increase the large volumes of fast moving air to the appropriate temperature. This results in significant NOx emissions.
As set forth in greater detail below, the present disclosure sets forth an improved burner assembly and system embodying advantageous alternatives to the conventional devices and methods discussed above.